"""
自定义的分页组件， 以后如果想要使用这个分页组件， 你需要做如下几件事
在视图函数中：
    def pretty_list(request):
        from ..utils.pagination import Pageination
        1.根据自己的情况去筛选自己的数据
        # .all() 表示Selecte * from 表  order by level desc;
        queryset = models.PrettyNum.objects.filter(**data_dict).order_by("-level")

        2.实例化分页对象
        page_object = Pageination(request, queryset)

        context = {
            "queryset": page_object.page_queryset,  # 分完页的数据
            "page_string":  page_object.html() # 页码
        }

        return render(request, "app_02/pretty_list.html", context)


在html中
    {% for obj in queryset %}

    {% endfor %}

    <ul class="pagination">
        {{ page_string }}
    </ul>

"""
from django.utils.safestring import mark_safe


class Pagination(object):
    def __init__(self, request, queryset, page_param="page", page_size=10, plus=5):
        """
        :param request:请求的对象
        :param queryset:符合条件的数据(根据这个数据给他进行分页处理)
        :param page_size:每页显示多少条数据
        :param page_param:在URL中传递的获取分页的参数，例如:/pretty/list/?page=12
        :param plus:显示当前页的 前或后几页(页码)
        """
        from django.http.request import QueryDict
        import copy
        query_dict = copy.deepcopy(request.GET)
        query_dict._mutable = True
        self.query_dict = query_dict
        self.page_param = page_param


        page = request.GET.get(self.page_param, "1")
        if page.isdecimal():
            page = int(page)
        else:
            page = 1

        self.page = page
        self.page_size = page_size

        self.start = (page - 1) * page_size
        self.end = page * page_size

        self.page_queryset = queryset[self.start:self.end]

        # 数据总条数
        total_count = queryset.count()

        # 总页码
        total_page_count, div = divmod(total_count, page_size)
        if div:
            total_page_count += 1
        self.total_page_count = total_page_count
        self.plus = plus


    def html(self):
        # 计算出，显示当前页的前五页， 后五页
        if self.total_page_count <= 2 * self.plus + 1:
            # 数据库数据量比较少， 都没有到达11页
            start_page = 1
            end_page = self.total_page_count
        else:
            # 数据库数量数据比较多，>11页
            # 当前页<5时：(极小值)
            if self.page <= self.plus:
                start_page = 1
                end_page = 2 * self.plus + 1
            else:
                # 当前页 > 5
                # 当前页+5 > 总页面
                if (self.page + self.plus) > self.total_page_count:
                    start_page = self.total_page_count - 2 * self.plus
                    end_page = self.total_page_count
                else:
                    start_page = self.page - self.plus
                    end_page = self.page + self.plus

        # 页码
        page_str_list = []
        """
            <li><a href="?page=1">1</a></li>
            <li><a href="?page=2">2</a></li>
            <li><a href="?page=3">3</a></li>
        """

        self.query_dict.setlist(self.page_param, [1])
        page_str_list.append('<li><a href="?page={}">首页</a></li>'.format(self.query_dict.urlencode()))

        # 上一页
        if self.page > 1:
            self.query_dict.setlist(self.page_param, [self.page - 1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [1])
            prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(prev)

        # 页面
        for i in range(start_page, end_page + 1):
            self.query_dict.setlist(self.page_param, [i])
            if i == self.page:
                ele = '<li class="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            else:
                ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
            page_str_list.append(ele)

        # 下一页
        if self.page < self.total_page_count:
            self.query_dict.setlist(self.page_param, [self.page + 1])
            next = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        else:
            self.query_dict.setlist(self.page_param, [self.total_page_count])
            next = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
        page_str_list.append(next)

        # 尾页
        self.query_dict.setlist(self.page_param, [self.total_page_count])
        page_str_list.append('<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))

        search_string = """
            <li>
                <form style="float: right;margin—right:2px" method="get" action="/app_02/pretty/list/">
                    <div class="input-group" style="width: 200px">
                        <input class="form-control" type="text" name="page"
                               style="position: relative;float: right;display: inline-block;width: 150px;border-radius:0;" placeholder="页码">
                        <span class="input-group-btn">
                        <button style="border-radius:0" type="submit" class="btn btn-default">跳转</button>
                        </span>
                    </div>
                </form>
            </li>
            """
        page_str_list.append(search_string)
        page_string = mark_safe("".join(page_str_list))
        return page_string

